src/Evented.js

class Evented {
    events = {}

    // constructor() {
    //     this.events = {}
    // }

    on(name, callback) {
        if (!this.events[name]) {
            this.events[name] = []
        }
        this.events[name].push(callback)
        return callback // for when called with function/arrow literal
    }

    off(name, callback = null) {
        if (this.events[name]) {
            if (callback) {
                this.events[name] = this.events[name].filter(
                    cb => cb !== callback
                )
            }
            if (this.events[name].length === 0 || !callback) {
                delete this.events[name]
            }
        }
    }

    emit(name, ...args) {
        if (this.events[name]) {
            this.events[name].forEach(callback => callback(...args))
        }
    }
}
export default Evented